Young women in South Africa have an annual HIV incidence of 6-10% and are a high priority group for combination HIV prevention, including HIV testing, condoms and risk reduction counseling, partner HIV testing, modest cash transfers and oral pre-exposure prophylaxis (PrEP). PrEP has demonstrated efficacy (44-75% in randomized trials, >90% with high adherence) and is user-controlled, yet young African women in two blinded, placebo-controlled trials of PrEP had very low adherence, resulting in no demonstrated effectiveness in the context of very high HIV incidence. These results raise key questions for HIV prevention in women about perception of low HIV acquisition risk, lack of motivation in a placebo-controlled trial, barriers to taking a daily pill, partner support or lack, or low interestin HIV prevention. Programs that deliver combination prevention to young South African women need a better understanding of what motivates them to use combination prevention, how they recognize their risk, evaluate evidence and apply this to adoption of prevention strategies. We will conduct formative research about how women understand their risks and the role of intimate partners, which we hypothesize, are central determinants of intention, motivation, adoption of and adherence to HIV prevention strategies. We will use complimentary frameworks of the Information-Motivations-Behavior (IMB) skills model for qualitative inquiry and behavioral economics (BE) for quantitative approaches to identify levers to change prevention decisions and develop practical messaging and interventions. We will use qualitative methods and experimental HIV risk vignette surveys among young HIV-negative women in Cape Town, South Africa to assess risk perception and motivations to adopt HIV prevention interventions. Findings will inform development of a pilot intervention designed to provide proof of concept that an intervention based on better communication about risk and partner engagement facilitates uptake of combination prevention including PrEP, and a short-lived modest cash incentive conditional on presence of detectable PrEP drug levels, will enhance persistent adherence among women initiating PrEP. The intervention to improve HIV risk evaluation and partner involvement for HIV prevention adoption, including CCI for PrEP adherence, will be evaluated in a cohort of 100 HIV-negative women in Cape Town. Our Specific Aims are to: Aim 1: Conduct formative research about male partners, related social factors and motivators that facilitate young South African women's uptake of and adherence to HIV prevention. Aim 2: Pilot strategies for testing the partners of young South African women and evaluate whether partner testing is associated with uptake of prevention by women. Aim 3: Implement a prevention intervention among young South African women using research findings about risk evaluation and other motivators and assess whether these interventions together with short-term CCI will enhance PrEP uptake and adherence in the presence or absence of partner involvement. These knowledge gaps must be addressed for future trials of biomedical prevention strategies and implementation of combination prevention with effective interventions for young African women.